Research activity involving the use of electron paramagnetic resonance techniques and spin trapping to investigate the role of oxygen free radicals as well as free radicals of other compounds has increased significantly in the last few years. Areas of biomedical research under active investigation in the group of users utilizing the present ESR instrument include: A) the involvement of oxygen free radicals in damage to heart and brain during ischemia/reperfusion induced tissue injury and the role of leucocyte activation in this process; B) the involvement of oxygen free radicals in the metabolism of paraquat; C) the role of free radical intermediates in ethanol cocaine, chlorohydrocarbon anesthetics, and aromatic amine carcinogen metabolism and in vitamin K dependent carboxylation of glutamate in target proteins; D) the role of oxygen free radicals and singlet oxygen in oxidative damage to DNA during carcinogenesis; and E) the role of oxygen free radicals in lipid peroxidation mediated damage to the eye. Research activity on the various projects are funded by 7 NIH grants and by 4 other granting agencies. Currently there are 8 principle investigators, 3 postdoctorates (2 more being recruited), 1 graduate student and 5 technicians using one functioning ESR unit. This has caused a bottleneck of research activity dependant upon one ESR instrument and has decreased the available development type research time on the instrument to nearly zero. The large research work load on one instrument is causing a slow down of research and will seriously limit future research in many extremely active promising areas and therefore we are asking for funds to purchase another ESR unit.